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191.
192.
月地转移轨道快速设计与特性分析 总被引:1,自引:0,他引:1
对采用直接大气再入方式的月地转移轨道,考虑大气再入界面参数和地面落点位置约束,提出了一种基于双二体模型的快速设计方法。该方法分为内外两层迭代循环,内层循环使月心段轨道和地心段轨道在月球影响球边界处连续,并采用Lambert问题与Newton-Raphson法相集合的方法求解满足再入角约束的地心段轨道参数;外层循环通过调整地心段轨道倾角和轨道置入时间使月地转移轨道满足地面落点位置约束。分析表明,存在四种类型的月地转移轨道满足大气再入界面约束,分别为降 降型、降 升型、升 降型和升 升型。在此基础上,对四种类型月地转移轨道的近地点地心距、置入分布点、再入点分布等特性进行了分析。仿真结果验证了所提出方法的有效性。 相似文献
193.
近年来随着金银珠宝类消费的增长,廊坊市也成为珠宝企业炙手可热的目标市场。钻石宝贝是一家电子商务和实体体验店相结合的珠宝品牌,为了帮助钻石宝贝顺利进入廊坊市场,通过市场调查,获得了消费者特征和偏好等信息,并提出了产品、价格、渠道、促销等营销策略建议。 相似文献
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195.
Three major cusp models are systematically compared with low-resolution (large-scale) and high-resolution (fine-scale) low-altitude observations. Those models are (a) global magnetohydrodynamics (MHD) models (including MHD+drift models), (b) turbulent/diffusive entry models, and (c) direct flowing entry models. Although low-resolution data are mostly consistent with MHD models, high-resolution data mostly contradicts them. The data instead supports the other models in which the cusp is considered as a local `extra' open region. This is a good lesson to us: past supportive `tests' of MHD cusp models might have essential flaws in the methodology, and high-resolution data is necessary even for large-scale modelings. 相似文献
196.
以中国矿业大学教师公寓小高层住宅项目为例,介绍了低温热水地面辐射采暖系统的特点及施工要点,并进行了能效分析,根据实际运行情况对该系统进行了分析和总结。达到了预期的设计目的,提高和改善了供暖使用功能,具有较高的推广价值。 相似文献
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198.
Michael Bender Galina Dick Maorong Ge Zhiguo Deng Jens Wickert Hans-Gert Kahle Armin Raabe Gerd Tetzlaff 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A GNSS water vapour tomography system developed to reconstruct spatially resolved humidity fields in the troposphere is described. The tomography system was designed to process the slant path delays of about 270 German GNSS stations in near real-time with a temporal resolution of 30 min, a horizontal resolution of 40 km and a vertical resolution of 500 m or better. After a short introduction to the GPS slant delay processing the framework of the GNSS tomography is described in detail. Different implementations of the iterative algebraic reconstruction techniques (ART) used to invert the linear inverse problem are discussed. It was found that the multiplicative techniques (MART) provide the best results with least processing time, i.e., a tomographic reconstruction of about 26,000 slant delays on a 8280 cell grid can be obtained in less than 10 min. Different iterative reconstruction techniques are compared with respect to their convergence behaviour and some numerical parameters. The inversion can be considerably stabilized by using additional non-GNSS observations and implementing various constraints. Different strategies for initialising the tomography and utilizing extra information are discussed. At last an example of a reconstructed field of the wet refractivity is presented and compared to the corresponding distribution of the integrated water vapour, an analysis of a numerical weather model (COSMO-DE) and some radiosonde profiles. 相似文献
199.
G. Kminek J.D. Rummel C.S. Cockell R. Atlas N. Barlow D. Beaty W. Boynton M. Carr S. Clifford C.A. Conley A.F. Davila A. Debus P. Doran M. Hecht J. Heldmann J. Helbert V. Hipkin G. Horneck T.L. Kieft G. Klingelhoefer M. Meyer H. Newsom G.G. Ori J. Parnell D. Prieur F. Raulin D. Schulze-Makuch J.A. Spry P.E. Stabekis E. Stackebrandt J. Vago M. Viso M. Voytek L. Wells F. Westall 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
In this paper we present the findings of a COSPAR Mars Special Regions Colloquium held in Rome in 2007. We review and discuss the definition of Mars Special Regions, the physical parameters used to define Mars Special Regions, and physical features on Mars that can be interpreted as Mars Special Regions. We conclude that any region experiencing temperatures > −25 °C for a few hours a year and a water activity > 0.5 can potentially allow the replication of terrestrial microorganisms. Physical features on Mars that can be interpreted as meeting these conditions constitute a Mars Special Region. Based on current knowledge of the martian environment and the conservative nature of planetary protection, the following features constitute Mars Special regions: Gullies and bright streaks associated with them, pasted-on terrain, deep subsurface, dark streaks only on a case-by-case basis, others to be determined. The parameter definition and the associated list of physical features should be re-evaluated on a regular basis. 相似文献
200.
S. Choy C. Wang K. Zhang Y. Kuleshov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The March 2010 Melbourne storm is used as a case study to examine the potential of using Global Positioning System (GPS) observations for studying the precipitable water vapour (PWV) field. The Victorian statewide GPS infrastructure network, i.e. GPSnet, was used in this study. GPSnet is currently the only statewide and densest GPS infrastructure network in Australia, which provides an excellent opportunity to examine the distribution of water vapour as the severe weather system passed over the state. Data from 15 GPSnet stations were processed over a one-week period, i.e. a few days prior to and after the storm passage, during which the course of the storm extended from the west to the southeast corner of the state. In addition, data from two radiosonde sites of the Australian Bureau of Meteorology Upper Air Network were used to compare and validate the GPS derived PWV measurements. The findings demonstrate that there is strong spatial and temporal correlation between variations of the ground-based GPS-PWV estimates and the passage of the storm over the state. This is encouraging as the ground-based GPS water vapour sensing technique can be considered as a supplemental meteorological sensor in studying severe weather events. The advantage of using ground-based GPS-PWV technique is that it is capable of providing continuous observation of the storm passage with high temporal resolution. The spatial resolution of the distribution of water vapour is dependent on the geographical location and density of the GPS stations. 相似文献